scholarly journals Influence of the Surface Layer when the CMT Process Is Used for Welding Steel Sheets Treated by Nitrooxidation

10.14311/1528 ◽  
2012 ◽  
Vol 52 (2) ◽  
Author(s):  
I. Michalec ◽  
M. Marônek
Keyword(s):  
Surface Layer ◽  
Negative Impact ◽  
Welding Process ◽  
Treatment Method ◽  
Metal Transfer ◽  
Cold Metal Transfer ◽  
Steel Sheets ◽  
Welding Steel ◽  
Joint Quality ◽  
Cold Metal

Nitrooxidation is a non-conventional surface treatment method that can provide significantly improved mechanical properties as well as corrosion resistance. However, the surface layer is a major problem during the welding process, and welding specialists face many problems regarding the weldability of steel sheets. This paper deals with the properties of a nitrooxidized surface layer, and evaluates ways of welding steel sheets treated by nitrooxidation using a Cold Metal Transfer (CMT) process. The limited heat input and the controlled metal transfer, which are considered as the main advantage of the CMT process, have a negative impact on weld joint quality. An excessive amount of porosity is observed,probably due to the high content of nitrogen and oxygen in the surface layer of the material and the fast cooling rate of the weld pool.

Cold Metal Transfer Spot Joining of AA6061-T6 to Galvanized DP590 Under Different Modes

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
HaiYang Lei ◽  
YongBing Li ◽  
Blair E. Carlson ◽  
ZhongQin Lin
Keyword(s):  
Heat Input ◽  
Mechanical Performance ◽  
Welding Process ◽  
High Strength ◽  
Metal Transfer ◽  
Cold Metal Transfer ◽  
Spot Joining ◽  
Predrilled Hole ◽  
Joint Quality ◽  
Cold Metal

In order to meet the upcoming regulations on greenhouse gas emissions, aluminum use in the automotive industry is increasing. However, this increase is now seen as part of a multimaterial strategy. Consequently, dissimilar material joints are a reality, which poses significant challenges to conventional fusion joining processes. To address this issue, cold metal transfer (CMT) spot welding process was developed in the current study to join aluminum alloy AA6061-T6 as the top sheet to hot dip galvanized (HDG) advanced high strength steel (AHSS) DP590 as the bottom sheet. Three different welding modes, i.e., direct welding (DW) mode, plug welding (PW) mode, and edge plug welding (EPW) mode were proposed and investigated. The DW mode, having no predrilled hole in the aluminum top sheet, required concentrated heat input to melt through the Al top sheet and resulted in a severe tearing fracture, shrinkage voids, and uneven intermetallic compounds (IMC) layer along the faying surface, leading to poor joint properties. Welding with the predrilled hole, PW mode, required significantly less heat input and led to greatly reduced, albeit uneven, IMC layer thickness. However, it was found that the EPW mode could homogenize the welding heat input into the hole and thus produce the most stable welding process and best joint quality. This led to joints having an excellent joint morphology characterized by the thinnest IMC layer and consequently, best mechanical performance among the three modes.

scholarly journals Influence of post weld heat treatment on tensile properties of cold metal transfer (CMT) arc welded AA6061-T6 aluminium alloy joints

2019 ◽  
Vol 28 (1) ◽  
pp. 135-145 ◽  
Author(s):  
Addanki Ramaswamy ◽  
Sudersanan Malarvizhi ◽  
Visvalingam Balasubramanian
Keyword(s):  
Heat Treatment ◽  
Tensile Properties ◽  
Gas Metal Arc Welding ◽  
Weight Ratio ◽  
Welding Process ◽  
Metal Transfer ◽  
Post Weld Heat Treatment ◽  
Cold Metal Transfer ◽  
Cold Metal ◽  
Weld Heat

AbstractAluminium alloys of 6xxx series are widely used in the fabrication of light weight structures especially, where high strength to weight ratio and excellent weld-ability characteristics are desirable. Gas metal arc welding (GMAW) is the most predominantly used welding process in many industries due to the ease of automation. In this investigation, an attempt has been made to identify the best variant of GMAW process to overcome the problems like alloy segregation, precipitate dissolution and heat affected zone (HAZ) softening. Thin sheets of AA6061-T6 alloy were welded by cold metal transfer (CMT) and Pulsed CMT (PCMT). Among the two joints, the joint made by PCMT technique exhibited superior tensile properties due to the mechanical stirring action in the weld pool caused by forward and rearward movement of the wire along with the controllable diffusion rate at the interface caused by shorter solidification time. However, softening still exists in the welded joints. Further to increase the joint efficiency and to minimize HAZ softening, the joints were subjected to post weld heat treatment (PWHT). Approximately 10% improvement in the tensile properties had been observed in the PWHT joints due to the nucleation of strengthening precipitates in the weld metal and HAZ.

Studies on cold metal transfer welding of aluminium alloy 6061-T6 using ER 4043

2020 ◽  
Vol 234 (7) ◽  
pp. 924-937
Author(s):  
R Pramod ◽  
N Siva Shanmugam ◽  
CK Krishnadasan
Keyword(s):  
Mechanical Properties ◽  
Aluminium Alloy ◽  
Pressure Vessel ◽  
Weld Zone ◽  
Welding Process ◽  
Metal Transfer ◽  
Welding Parameter ◽  
Cold Metal Transfer ◽  
Cold Metal ◽  
Alloy 6061

Aluminium alloy 6061-T6 is utilized in aerospace industry for developing pressure vessel liner. Cold metal transfer is a promising welding process used in fabricating aluminium structures. The present work is focussed to achieve an optimum welding parameter for joining a 3.5-mm thick pressure vessel and to examine the mechanical properties and metallurgical nature of the weldment. The welded joint was evaluated as defect free using radiography test. The joint efficiency (66.61%) and measured microhardness of weldment (59.78 HV) exhibited promising results. The effect of grain coarsening in the heat affected zone (HAZ) and weld zone is attributed to the thermal gradients during welding. Dissipation of small amounts of strengthening elements Si and Mg during welding leads to reduction in mechanical properties. X-ray diffraction peaks revealed the presence of intermetallic Al–Si and Fe–Si in the weld zone. Fractography examination confirms the ductile type of failure in the fractured surface of the tensile samples.

Enhanced Performance of Steel-Aluminium Cast Nodes through Cold Metal Transfer

2013 ◽  
Vol 765 ◽  
pp. 736-740
Author(s):  
Stephan Ucsnik ◽  
Rudolf Gradinger ◽  
Almedin Becirovic ◽  
Andreas Waldhör
Keyword(s):  
Load Transfer ◽  
Welding Process ◽  
Metal Transfer ◽  
Uniaxial Tensile ◽  
Cold Metal Transfer ◽  
Cast Aluminium ◽  
Pull Out ◽  
Macro Scale ◽  
Cold Metal ◽  
Scale Roughness

At present, enhancement of hybrid metal joints for tensile pull-out load through overlap surfaces with a macro-scale roughness is one scope of research. The macro-scale roughness is established through the modified arc-welding process, called “cold metal transfer pin” (CMT-pin), which enables repetitive manufacturing of arrays of metal reinforcements (pins) on parent metal surfaces.Hybrid metal joints between parent steel sleeves and cast aluminium alloy have been investigated. Joint surfaces of parent steel sleeves, which have cylindrical cross-sections, are modified by cylinder and ballhead pins. Cast metal joints were tested under uniaxial tensile loading. At the same time, their load transfer behaviour was determined. Results of tensile tests of hybrid metal joints with different kinds of pins, as well as with different amounts of pins are presented. Comparisons with reference joints without pins or with steel sleeves containing a harmonious triangular polygon cross-section ("P3G") and endings with an enlarged diameter are carried out.The results show an enhanced load transfer performance in the case of hybrid metal joints with pins, as well as enhanced performance measures compared to reference joints. It is also shown that the pin quantity has a major impact on the ultimate joint strength and the irreversible energy absorption density. The use of a certain quantity of pins leads to a change of the failure shape of the joints, which includes steel sleeve pull-out and pin shear to rupture of the cast aluminium.

scholarly journals Complex Behavior of Droplet Transfer and Spreading in Cold Metal Transfer

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Shuai Yang ◽  
Yanfeng Xing ◽  
Fuyong Yang ◽  
Juyong Cao
Keyword(s):  
Control Method ◽  
Short Circuit ◽  
Continuous Process ◽  
Welding Process ◽  
Intelligent Manufacturing ◽  
Metal Transfer ◽  
Droplet Spreading ◽  
Cold Metal Transfer ◽  
Cmt Welding ◽  
Cold Metal

In intelligent manufacturing, an intelligent control method of welding process is an important process of intelligent welding manufacturing technology (IWMT). Metal transfer is a key factor to control the welding process. Metal transfer and droplet spreading are of vital importance for welding formation. A new theoretical model of cold metal transfer (CMT) in short-circuit transfer mode is proposed in this paper. In this model, the CMT welding process is regarded as a continuous process of arc heating, mass transfer, short-circuit, and spreading, and the relations between these processes are analyzed. The calculation equations used by the model can analyze the welding formation clearly and simplify the complex welding process into continuous physical behavior. The predicted welding width shows good agreement with the measurement results. The mechanism of increased welding width is also comprehensively analyzed. Results have a certain guiding effect on aluminum alloy welding process control.

scholarly journals Process variable optimization in the cold metal transfer weld repair of aerospace ZE41A-T5 alloy using central composite design

2019 ◽  
Vol 105 (11) ◽  
pp. 4827-4835 ◽  
Author(s):  
O. T. Ola ◽  
R. L. Valdez ◽  
K. M. Oluwasegun ◽  
O. A. Ojo ◽  
K. Chan ◽  
...  
Keyword(s):  
Central Composite Design ◽  
Desirability Function ◽  
Welding Process ◽  
Metal Transfer ◽  
Fusion Welding ◽  
Complete Fusion ◽  
Cold Metal Transfer ◽  
Cold Metal ◽  
Application Specific ◽  
Central Composite

AbstractThe pulsed cold metal transfer (CMT+P) process was evaluated for the repair of aerospace structural components made from ZE41A-T5 magnesium alloy. The choice of welding variables was considered to be unique for the material type, weld design and geometry, and application-specific requirements. A design of experiment (DOE) method based on a rotatable 3D central composite design (CCD) was used to systematically establish relationships between independent welding variables and the resultant output variables of the CMT+P process, including the development of mathematical models based on second-order polynomial. A multiple response desirability function approach was then used for process optimization. The CMT+P process produced high-quality welds in the alloy. Welding process variables were established to produce desired weld penetration and weld reinforcement and complete fusion with minimal weld defects. Optimal domains of the independent variables were achieved; where the welds comply with the application-specific (repair of gearbox housing) requirements and acceptable class A weld quality of the aerospace fusion welding standard AWS D17.1.

Cold-Metal-Transfer Arc Joining of Al 6K32 Alloy to Steel Sheets

2013 ◽  
Vol 334-335 ◽  
pp. 247-251 ◽  
Author(s):  
Min Jung Kang ◽  
Cheol Hee Kim
Keyword(s):  
Automotive Industry ◽  
Arc Welding ◽  
Intermetallic Phase ◽  
Metal Transfer ◽  
Cold Metal Transfer ◽  
Steel Sheets ◽  
Welding Technology ◽  
Coating Type ◽  
Cold Metal ◽  
Interface Layers

In the arc joining of dissimilar metals, such as steel and Al alloys, a brittle intermetallic phase is formed at the interface. The thickness of this phase should be minimized because it causes solidification cracking. Cold metal transfer (CMT) arc welding technology is widely used throughout the automotive industry because of low spatter formation and heat input. A CMT arc was used to investigate arc joining between the Al 6K32 alloy and mild steel sheets. The behaviors of the interface layers were analyzed on the basis of filler wires and the coating type of the steel sheets. The thickness of the intermetallic phase was maintained under 10 μm and increased joint strength was achieved by selecting the appropriate filler wire and coating type.

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